Electrical bushing having a two-chambered fluid expansion system

ABSTRACT

Oil-filled bushing having two arc-shaped oil expansion chambers located near the center of the bushing. One chamber is located generally on one side of the bushing conducting lead and the other chamber is located generally on the other side of the conducting lead. Openings in the two chambers are interconnected by tubing to permit the transfer of oil and gas therebetween. One chamber contans another opening which allows oil contained within the bushing to enter this chamber. The boundaries of the chambers are shaped to permit oil flow between the chambers when the bushing is mounted at different angles.

United States Patent 191 Hildenbrand Sept. 9, 1975 [54] ELECTRICAL BUSHING HAVING A 1,129,616 10/1968 United Kingdom 174 11 BH 97,524 l/l92'3 Switzerland 174/1 l BI'I SYSTEM Primary Exam1nerLaram1e E. Askm, [75] Inventor: gerry L. Hildenbrand, Portland, Attorney Agent or Hanway reg.

[73] Assignee: Westinghouse Electric Corporation, [57] ABSTRACT Pittsburgh, Oil-filled bushing having two arc-shaped oil expansion [22] Filed: Oct 22, 1974 chambers located near the center of the bushing. One

chamber is located generally on one side of the bush- PP N04 516,934 ing conducting lead and the other chamber is located generally on the other side of the conducting lead. 52 US. Cl :5. 174/12 BH; 174/31 R Openings in the Chambers are interconnected by 51 Int. c1. H01B 17/26 tubing to Permit the transfer of Oil a gas tnerebe- [58] Field of Search n 174/ BH 12 R, 12 BH, tween. One chamber contans another opening which 174/14 3H 18, 31 R allows oil contained within the bushing to enter this chamber. The boundaries of the chambers are shaped [56] References Cited to permit oil flow between the chambers when the bushing is mounted at different angles.

12 Claims, 5 Drawing Figures PATENTEUSEP 9 i975 sum 1 or 2 Ill will;

PATENTEDSEP 91s 3 SHEET 2 OF 2 ELECTRICAL BUSHING HAVING A TWO-CHAMBERED FLUID EXPANSION SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates. in general, to electrical bushings and. more specifically. to oil-filled bushings suitable for horizontal attachment to electrical apparatus.

2. Description of the Prior Art Large oil-filled condenser bushings require an expansion chamber located on top of the upper insulating structure to accommodate changes in oil volume due to temperature variations. A gas space exists above the oil level when the oil does not completely fill the expansion chamber. This gas space must be contained in the expansion chamber rather than in another portion of the bushing to assure the required dielectric strength of the insulating materials within the bushing. Therefore, bushings having the oil-gas interface normally located within the expansion chamber must be mounted in a vertical or near vertical position.

Oil-filled bushings have been constructed for horizontal or near horizontal mounting. Such bushings are equipped with an external expansion chamber which is mounted near the center of the bushing and above the oil contained within the bushing. Suitable tubing connects the oil in the bushing with the center mounted expansion chamber. Since such an expansion chamber is located substantially away from the exterior surface of the bushing, it is fairly vulnerable to abuse and destruction. In addition, the remote" location of this prior art expansion chamber arrangement requires more oil to fill the bushing assembly.

One of the main differences between oil-filled bushings constructed for horizontal or vertical mounting lies in the arrangement for providing the required oil-to-gas interface which allows oil volume changes. According to the prior art. the preferred oil expansion chamber arrangement which is located on the top of the bushing may not be used for horizontal mounting. Thus, separate condenser bushing designs must be developed to accommodate both horizontal and vertical mounting requirements. Therefore, it is desirable, and it is an object of this invention. to provide an oil-filled bushing which, without significant modification, can be mounted in either the vertical or the horizontal direction. It is also desirable, and it is another object of this invention, to provide a bushing suitable for horizontal mounting in which the oil expansion chamber is better protected than that afforded by the prior art arrangements.

SUMMARY OF THE INVENTION There is disclosed herein a new and useful oil-filled electrical bushing which is suitable for mounting in the vertical direction. the horizontal direction. or any di rection therebetween. The bushing disclosed herein also has an oil expansion system which is better protected than oil expansion systems of the prior art which could be used for horizontally mounted bushings. The bushing includes first and second arc-shaped expansion chambers positioned around the bushing mounting assembly and near to the longitudinal center of the bushing. The first chamber is partially defined by an outer surface which is obliquely oriented with respect to the longitudinal axis of the bushing. A similarly oriented outer surface defines the outer surface of the second chamber. The openings in the outer surfaces of the two chambers are interconnected by tubing to permit the passage of oil and gas between the two chambers. These openings are positioned on the outer surfaces of the chambers at locations which provide for the complete filling or removal of oil. as the case may be. when the oil expands and contracts without passing any gas before the oil has been completely moved. This type of operation exists for various mounting angles of the bushing. The opening in the upper chamber is located in the outer surface thereof at the position of maximum radial distance from the bushing conducting lead. The opening in the lower chamber is positioned at a location which is dependent upon the mounting angle of the bushing. Another opening in the upper chamber allows for the oil within the bushing to communicate directly with the upper chamber. The chambers are located between a discshaped flange and a disc-shaped plate of the bushing supporting structure.

BRIEF DESCRIPTION OF THE DRAWING Further advantages and uses of this invention will become more apparent when considered in view of the following detailed description and drawing. in which:

FIG. 1 is a view of a condenser bushing constructed according to this invention;

FIG. 2 is an enlarged view of the oil expansion system of the bushing shown in FIG. I;

FIG. 3 is a cross-sectional view taken along the line lIl-III of FIG. 2;

FIG. 4 is a schematic representation of the condition of the oil expansion system when the oil temperature is relatively low; and

FIG. 5 is a schematic representation of the condition of the oil expansion system when the oil temperature is relatively high.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout the following description. similar reference characters refer to similar elements or members in all of the figures of the drawing.

Referring now to the drawing, and to FIG. I in particular, there is shown an electrical condenser bushing constructed according to one embodiment of this invention. The bushing includes the lower porcelain insulating structure 10', the upper porcelain insulating structure 12, and the supporting structure 14 which is located generally between the insulating structures 10 and 12. The interior end 16 and the exterior end 18 of the bushing are adapted for connection of the necessary electrical leads when the bushing is connected for operation. The enclosure 20 houses the spring mechanism of the bushing which produces the proper stresses on the components of the bushing to maintain oil-tight seals between the supporting structure I4 and the insulating structures 10 and 12. The enclosure 20 takes the place of the expansion cap used normally in prior art condenser bushings. Since the enclosure 20 is not required to contain an appreciable amount of oil. the dimensions of the enclosure 20 are only required to be large enough to enclose the spring assembly therein.

The supporting structure 14 includes the disc-shaped mounting flange 22 and the disc-shaped plate 24, between which the oil expansion system 26 is located. The oil expansion system 26 is positioned near the center ofthe bushing and is recessed between the plates 22 and 24 for protection from damage and to reduce the space required for mounting the bushing. The oil expansion system 26 contains the oil-to-gas interface of the bushing which is necessary to provide a means for adequately allowing the expansion of the oil dielectric of the bushing. The level of the oil in the oil expansion system 26 is indicated by the oil level gauge 28.

FIG. 2 is an enlarged view of the oil expansion system 26 shown in FIG. I. The supporting structure 14 includes the metallic cylindrical member 30 which extends from the disc-shaped mounting flange 22 to the lower porcelain insulating structure and to the discshaped plate 24. The flange 22 provides means for connecting the bushing to the enclosure of the electrical apparatus it is associated with. The plate 24 provides a surface to which the porcelain insulating structure 12 is mounted and sealed. The oil expansion system 26 includes the upper arc-shaped chamber 32 and the lower arc-shaped chamber 34.

FIG. 3 is a cross-sectional view of the oil expansion system 26 taken generally along the line lIllll of FIG. 2. Referring to both FIGS. 2 and 3, the upper chamber 32 and the lower chamber 34 are interconnected by the tubing 36 which is connected to the outer surfaces 38 and 40 of the chambers 32 and 34, respectively. The

guard 42, which is shown in FIG. 2 but not in FIG. 3 for the purpose of clarity, is used to protect the tubing from accidental damage. It is within the contemplation of this invention that the guard 42 may include a radial portion extending around the tube to substantially completely enclose the tubing 36. A voltage tap socket 44 and an oil sampling valve 46 extend from the cylindrical member for connecting appropriate apparatus to the bushing. A longitudinal conducting lead 48 extends through the bushing and is surrounded by a condenser-type insulating structure 50. The oil gauge 28 is mounted on the side wall ofthe upper chamber 32 and may be of the float-level indicating type. Dcpending on the mounting angle of the bushing, .it may be desirable to rotate the gauge 28 to provide an accurate reading of the actual oil level in relation to the nominal oil level maintained during normal bushing operation.

The upper chamber 32 and the lower chamber 34 are defined at each end by the flange 22 and by the plate 24. The inner surfaces of the chambers 32 and 34 are defined by the cylindrical member 30. The radially extending sides of the chambers 32 and 34 may be constructed of any suitable material. such as copper or stainless steel.

The outer surfaces 38 and of the chambers 32 and 34, respectively, are substantially arc-shaped and extend around the cylindrical member 30 and the conducting lead 48. In addition to being arc-shaped, the

outer surfaces 38 and 40 are obliquely aligned with the longitudinal axis of the bushing. In other words, the radial distances from the conducting lead 48 to the outer surfaces 38 and 40 are smaller at the flange 22 than at the plate 24. The purpose of this inclined or oblique orientation of the outer surfaces is to provide an area thereon which, with a particular mounting angle, is at least as high as any other area on the outer surface of the particular chamber.

The tubing 36 is connected to the openings in the upper chamber 32 and in the lower chamber 34 for the purpose of allowing oil and gas to communicate between the chambers. The opening 52 in the cylindrical member 30 permits communication between the oil in the insulating structure which is located in the interior of the bushing and the oil contained within the upper chamber 32.

FIGS. 4 and 5 may be used to explain the operation of the two-chambered oil expansion system of this invention. The bushing illustrated schematically in FIG. 4 is mounted in the horizontal direction. The oil contained within the cylindrical member 30 of the bushing communicates with the chamber 32 through the opening 52. When the oil temperature is below its nominal value, the oil level 58 is positioned within the chamber 32 as shown in FIG. 4. The gas 62 occupies the remainder of the chamber 32, and by means of the tubing 36 and the openings 64 and 66, occupies the chamber 34 as also shown in FIG. 4. When the temperature of the oil 60 increases, the oil level 58 rises in the chamber 32. If the oil temperature raises sufficiently, the oil will be transferred through the tubing 36 to the bottom of the chamber 34. The oil will fill the chamber 34 up to a level 58' as shown in FIG. 5 when the oil temperature reaches its maximum value. When the oil temperature decreases, the oil in the chamber 34 is drawn back into the chamber 32 and into the cylindrical member 30 of the bushing.

The opening 64 in the chamber 32 is positioned at the uppermost portion of the chamber 32 to prevent any oil from being transferred through the tubing 36 until the chamber 32 is completely filled with oil. Similarly. the opening 66 in the lower chamber 34 is positioned at the lowermost position of the chamber 34 to prevent any oil from remaining in the chamber 34 after it has been withdrawn therefrom due to a decrease in oil temperature. The inclined angles of the outer surfaces of the chambers 32 and 34 permit the openings 64 and 66 to retain this relationship even when the bushing is mounted a few degrees above the horizontal position. When the bushing is mounted above the horizontal position by more than the amount of inclination of the outer surface 40 of the lower chamber 34, it is desirable to connect the tubing 36 to the opening 68 instead of to the opening 66. This assures that the opening in the chamber 34 which communicates with the opening 64 in the chamber 32 is at the lowest position in the chamber 34 for the particular mounting angle. For convenience of changing the tubing 36, fittings located at the openings 66 and 68 may be permanently installed on the lower chamber 34 and the unused fitting may be plugged. It is also within the contemplation of this invention that a wye may be placed in the lower portion of the tubing 36 with one branch of the wye connected to the opening 68 and the other branch of the wye connected to the opening 66. Thus, with this type of arrangement, the tubing would not have to be changed with different mounting angles.

When the tubing 36 is connected either directly to the opening 68, or through a wye arrangement to both the openings 66 and 68 in the chamber 34, the bushing may be mounted at an angle up to and including the angle acquired when'mounted in the fully vertical position. The oil level 58 would not be parallel to the axis of the bushing when the mounting angle is other than horizontal. When the bushing is mounted in a vertical position, the pressure of the gas 62 maintains the oil level 58 below the opening 64 and out of the tubing 36 and the chamber 34 due to the hydrostatic pressure of the oil 60 in the bushing. However, when the temperature of the oil increases, the volume of the oil increases sufficiently to enter the opening 64 and the oil flows through the tubing 36 to the chamber 34. When the temperature of. the oil has decreased, the oil is drawn from the chamber 34, back through the tubing 36, and into the chamber 32. Thus. the oil expansion system 26 taught by this invention permits the mounting of the bushing at any angle between horizontal and vertical without any substantial change in the expansion system.. I

Since numerous changes may be made in the above described apparatus, and since different embodiments of the invention may be made without departing from the spirit thereof. it is intended that all of the matter contained in the foregoing description, or shown in the accompanying drawing, shall be'interpretcd-as illustrative rather than limiting.

I claim as my invention:

1. An electrical bushing having interior and exterior ends and containing a fluid dielectric, said bushing comprising:

a conducting lead;

means for insulating the conducting lead;

means for mounting the bushing to an electrical apparatus casing; and

first and second chambers located on the outside of the bushing and being rigidly attached to the mounting means,

said chambers being located generally on opposite sides of the conducting lead; and

said chambers being connected in flow communication relationship with each other and with the fluid in the bushing, with the flow communication relationship between the first and second chambers being through a first opening in the first chamber and a second opening in the second chamber, said first opening being located at the radially outermost portion of the first chamber, and said second opening being located in the outer surface of the second chamber. 1

2. The electrical bushing of claim 1 wherein the first and second openings are located at substantially radially opposite positions in the bushing.

3. The electrical bushing of claim 1 wherein the flow communication relationship with the fluid in the bushing is established through a third opening, said third opening being located substantially in the radially innermost portion of the first chamber.

4. The electrical bushing of claim 3 wherein the third opening is also located near the portion of the first chamber which is located closest to the interior end of the bushing.

5. The electrical bushing of claim 1 wherein the means for mounting includes a disc-shaped flange positioned around a portion of the insulating means and the conducting lead, a cylindrical member extending from said flange toward the exterior end of the bushing, and a disc-shaped plate located at an end of the cylindrical member, with the first and second chambers located between the disc-shaped flange and plate.

6. The electrical bushing of claim 1 wherein the first chamber is generally arc-shaped and extends partially around a portion of the means for insulating and a portion ofthe conducting lead, with the radially outermost surface which defines the first chamber being obliquely oriented with the axis of the bushing to increase the radial distance of said surface from the conducting lead v ;6 as said surface progresses toward the exterior end of the bushing. l f

7. The electrical bushing of claim 1 wherein the second chamber is generally arc-shaped and extends partially around a portion of the means for insulating and a portion of the conducting lead, with the outer surface which defines the second chamber being obliquely oriented with the axis of the bushing to increase the radial distance of said surface from the conducting lead as said surface progresses toward the exterior end of the bushing. I

8. The electrical bushing of claim 1 wherein said second opening is located at the portion of the second chamber which experiences the greatest pressure head from the fluid dielectric for the particular mounting alignment of the bushing.

9. An electrical bushing having interior and exterior ends and containing a fluid dielectric, said bushing comprising:

a conducting lead;

means for insulating the conducting lead;

a disc-shaped flange positioned around the insulating means and the conducting lead;

a cylindrical member extending from said flange toward the exterior end of the bushing;

a disc-shaped plate located at an end of the cylindrical means;

a first arc-shaped chamber positioned generally on one side of the conducting lead and between the flange and the plate;

a second arc-shaped chamber positioned generally on the other side of the conducting lead and between the flangc and the plate;

said first and second chambers being partially dcfincd by outer arc-shaped surfaces which are obliquely aligned with the axis of the bushing, with the radius of the arc-shaped surfaces being greater when nearer to the disc-shaped plate; and

means for connecting in flow communication relationship an opening in the outer surface of the first chamber to an opening in the outer surface of the second chamber, said opening to the first chamber being located in the radially outermost portion of the outer surface of the first chamber, said opening to the second chamber being located radially opposite to the opening to the first chamber, with the longitudinal position of the opening to the second chamber being such as to be at the lowest level of any fluid contained within the second chamber for a predetermined bushing mounting angle;

said cylindrical member containing an opening therein for providing flow communication relationship between the bushing fluid dielectric and the first chamber.

10. An electrical bushing having interior and exterior ends and containing a fluid dielectric, said bushing comprising:

a conducting lead;

means for insulating the conducting lead;

means for mounting the bushing to an electrical apparatus casing; and

first and second chambers located adjacent to the mounting means, said chambers being connected in flow communication relationship with each other and with the fluid in the bushing:

said first and second chambers being connected in flow communication relationship with each other through a first opening in the first chamber and a second opening in the second chamber. said first opening being located substantially at the radially outermost portion of the first chamber and said second opening being located substantially at the radially outermost portion of the second chamber. with said first and second openings being located at substantially radially opposite positions in the bushing.

11. An electrical bushing having interior and exterior ends and containing a fluid dielectric, said bushing comprising:

a conducting lead;

means for insulating the conducting lead;

a disc-shaped flange positioned around a portion of the insulating means and the conducting lead;

a cylindrical member extending from said flange toward the exterior end of the bushing;

a disc-shaped plate located at an end of the cylindrical member; and

first and second chambers located between the discshaped flange and plate;

said chambers being connected in flow communication relationship with each other and with the fluid in the bushing.

12. An electrical bushing having interior and exterior ends and containing a fluid dielectric, said bushing comprising:

a conducting lead;

means for insulating the conducting lead;

means for mounting the bushing to an electrical apparatus casing; and

first and second chambers located adjacent to the mounting means, said chambers being connected in flow communication relationship with each other and with the fluid in the bushing;

with at least one of said chambers being generally are-shaped and extending partially around a portion of the means for insulating and a portion of the conducting lead, with the radially outermost surface which defines said arc-shapcd chamber being obliquely oriented with the axis of the bushing to increase the radial distance of said surface from the conducting lead as said surface progresses toward the exterior end of the bushing.

l= =l l l= l 

1. An electrical bushing having interior and exterior ends and containing a fluid dielectric, said bushing comprising: a conducting lead; means for insulating the conducting lead; means for mounting the bushing to an electrical apparatus casing; and first and second chambers located on the outside of the bushing and being rigidly attached to the mounting means, said chambers being located generally on opposite sides of the conducting lead; and said chamberS being connected in flow communication relationship with each other and with the fluid in the bushing, with the flow communication relationship between the first and second chambers being through a first opening in the first chamber and a second opening in the second chamber, said first opening being located at the radially outermost portion of the first chamber, and said second opening being located in the outer surface of the second chamber.
 2. The electrical bushing of claim 1 wherein the first and second openings are located at substantially radially opposite positions in the bushing.
 3. The electrical bushing of claim 1 wherein the flow communication relationship with the fluid in the bushing is established through a third opening, said third opening being located substantially in the radially innermost portion of the first chamber.
 4. The electrical bushing of claim 3 wherein the third opening is also located near the portion of the first chamber which is located closest to the interior end of the bushing.
 5. The electrical bushing of claim 1 wherein the means for mounting includes a disc-shaped flange positioned around a portion of the insulating means and the conducting lead, a cylindrical member extending from said flange toward the exterior end of the bushing, and a disc-shaped plate located at an end of the cylindrical member, with the first and second chambers located between the disc-shaped flange and plate.
 6. The electrical bushing of claim 1 wherein the first chamber is generally arc-shaped and extends partially around a portion of the means for insulating and a portion of the conducting lead, with the radially outermost surface which defines the first chamber being obliquely oriented with the axis of the bushing to increase the radial distance of said surface from the conducting lead as said surface progresses toward the exterior end of the bushing.
 7. The electrical bushing of claim 1 wherein the second chamber is generally arc-shaped and extends partially around a portion of the means for insulating and a portion of the conducting lead, with the outer surface which defines the second chamber being obliquely oriented with the axis of the bushing to increase the radial distance of said surface from the conducting lead as said surface progresses toward the exterior end of the bushing.
 8. The electrical bushing of claim 1 wherein said second opening is located at the portion of the second chamber which experiences the greatest pressure head from the fluid dielectric for the particular mounting alignment of the bushing.
 9. An electrical bushing having interior and exterior ends and containing a fluid dielectric, said bushing comprising: a conducting lead; means for insulating the conducting lead; a disc-shaped flange positioned around the insulating means and the conducting lead; a cylindrical member extending from said flange toward the exterior end of the bushing; a disc-shaped plate located at an end of the cylindrical means; a first arc-shaped chamber positioned generally on one side of the conducting lead and between the flange and the plate; a second arc-shaped chamber positioned generally on the other side of the conducting lead and between the flange and the plate; said first and second chambers being partially defined by outer arc-shaped surfaces which are obliquely aligned with the axis of the bushing, with the radius of the arc-shaped surfaces being greater when nearer to the disc-shaped plate; and means for connecting in flow communication relationship an opening in the outer surface of the first chamber to an opening in the outer surface of the second chamber, said opening to the first chamber being located in the radially outermost portion of the outer surface of the first chamber, said opening to the second chamber being located radially opposite to the opening to the first chamber, with the longitudinal position of the opening to the second chamber being such as to be aT the lowest level of any fluid contained within the second chamber for a predetermined bushing mounting angle; said cylindrical member containing an opening therein for providing flow communication relationship between the bushing fluid dielectric and the first chamber.
 10. An electrical bushing having interior and exterior ends and containing a fluid dielectric, said bushing comprising: a conducting lead; means for insulating the conducting lead; means for mounting the bushing to an electrical apparatus casing; and first and second chambers located adjacent to the mounting means, said chambers being connected in flow communication relationship with each other and with the fluid in the bushing; said first and second chambers being connected in flow communication relationship with each other through a first opening in the first chamber and a second opening in the second chamber, said first opening being located substantially at the radially outermost portion of the first chamber, and said second opening being located substantially at the radially outermost portion of the second chamber, with said first and second openings being located at substantially radially opposite positions in the bushing.
 11. An electrical bushing having interior and exterior ends and containing a fluid dielectric, said bushing comprising: a conducting lead; means for insulating the conducting lead; a disc-shaped flange positioned around a portion of the insulating means and the conducting lead; a cylindrical member extending from said flange toward the exterior end of the bushing; a disc-shaped plate located at an end of the cylindrical member; and first and second chambers located between the disc-shaped flange and plate; said chambers being connected in flow communication relationship with each other and with the fluid in the bushing.
 12. An electrical bushing having interior and exterior ends and containing a fluid dielectric, said bushing comprising: a conducting lead; means for insulating the conducting lead; means for mounting the bushing to an electrical apparatus casing; and first and second chambers located adjacent to the mounting means, said chambers being connected in flow communication relationship with each other and with the fluid in the bushing; with at least one of said chambers being generally arc-shaped and extending partially around a portion of the means for insulating and a portion of the conducting lead, with the radially outermost surface which defines said arc-shaped chamber being obliquely oriented with the axis of the bushing to increase the radial distance of said surface from the conducting lead as said surface progresses toward the exterior end of the bushing. 